ns.nic.lk has no MX records.
Question and response
Question
dig ns.nic.lk. MX
Answer
The response has no answer records.
Authority
lk. 3600 SOA ns.nic.lk. hostmaster.nic.lk. 2020161302 1800 900 2592000 3600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0